Process for preparing nonionic surfactants

ABSTRACT

A process for preparing a nonionic surfactant includes the steps of: cleaving at least one of the isopropylidene groups of an isopropylidene polyglycerol C 6  -C 22  -fatty acid or mono- or polyhydroxy fatty acid ester, by hydrolysis or ketal exchange, in the presence of acid, at a temperature in the range of about 20° C. to about 100° C., and at atmospheric, reduced or superatmospheric pressure, thereby regenerating hydroxyl groups on the polyglycerol; and recovering the resultant polyol ester nonionic surfactant. Such polyol ester surfactants are useful as emulsifiers, especially for preparing skin care or cosmetic formulations and paints and wood-preservation agents.

BACKGROUND OF THE INVENTION

The present invention relates to a process for preparing fatty acid ormono- or polyhydroxy fatty acid esters of polyglycerols fromintermediate fatty acid or mono- or polyhydroxy fatty acid esters ofisopropylidene derivatives of polyglycerols, in which specific processconditions for the preparation of the fatty acid esters of polyglycerolmust be followed.

The invention further relates to the use of the fatty acid esters ofpolyglycerol prepared by such process as nonionic surfactants, and toskin care and/or cosmetic formulations or ointments, paints andwood-protection agents, in which at least one such nonionic surfactantis used as an emulsifier.

It is already known to prepare fatty acid esters, for exampletetraesters, of polyglycerols by heating diglycerol for several dayswith a large excess of fatty acids, e.g., lauric, palmitic, stearic oroleic acid, but such esters are generally obtained in the form of brownsolid or oily compounds (see, e.g., C.A., 41, 2392 (1947)). As a resultof the long heating, only heavily contaminated products can be obtainedin very poor yields. The tetraesters thus prepared cannot be used assurfactants. The attempt has therefore been made to obtain thecorresponding compounds from isopropylidenediglycerol and stearylchloride in chloroform. However, the required amount of work involved isconsiderable, since after the reaction the mixture solidifies to give apaste, which must be taken up after 36 hours in benzene. After theaqueous solution is separated off and the organic phase is washed withwater, excess stearic acid must be removed by extraction with 10% sodiumbicarbonate solution, the organic phase must be dried over sodiumsulfate, and the solvent must be distilled off. The resulting residuehas to be recrystallized two or several times with alcohols. A furtherdisadvantage of this process is that hydrochlorides are formed in molarratios, which either have to be processed further or represent pollutingsubstances.

OBJECTS OF THE INVENTION

One object of the present invention is to provide an improved processfor preparing nonionic surfactants, in particular fatty acid esters ofpolyglycerols, from lower alkyl fatty acid or mono- or polyhydroxy fattyacid esters.

Another object of the invention is to provide a process for preparingfatty acid esters of polyglycerols which makes it possible to carry outselective esterifications of polyglycerols on a large industrial scale.

Another object of the invention is to provide a process for preparingfatty acid esters of polyglycerols wherein unreacted reagents orreaction byproducts can be at least partially recycled.

Another object of the invention is to provide substantially pure vicinalfatty acid diesters of diglycerol, fatty acid monoesters of the centralhydroxyl group of triglycerol, and fatty acid monoesters and diesters ofone or both of the central hydroxyl groups of tetraglycerol.

Another object of the invention is to provide nonionic surfactants thatare useful to prepare both water-in-oil and oil-in-water emulsions withhigh water content and good stability over time.

SUMMARY OF THE INVENTION

These and other objects of the invention are achieved by providing aprocess for preparing a nonionic surfactant, which comprises the stepsof:

(a) cleaving at least one of the isopropylidene groups of anisopropylidene polyglycerol C₆ -C₂₂ -fatty acid or mono- or polyhydroxyfatty acid ester, by hydrolysis or ketal exchange, in the presence ofacid, at a temperature in the range of about 20° C. to about 100° C.,and at atmospheric, reduced or superatmospheric pressure, therebyregenerating hydroxyl groups on the polyglycerol; and

(d) recovering the resultant polyol ester nonionic surfactant.

The invention further includes improved methods of preparing emulsionsusing the nonionic surfactants prepared by the foregoing process asemulsifiers. Also provided are skin care and cosmetic formulations,paints and wood-protection agents incorporating the nonionic surfactantsaccording to the invention as emulsifiers.

DETAILED DESCRIPTION

According to the invention, a process is provided for the preparation offatty acid or mono- or polyhydroxy fatty acid esters of polyglycerols.Hereinafter, the term "fatty acid ester" will include esters ofnon-hydroxylated, monohydroxylated and/or polyhydroxylated fatty acidsunless otherwise explicitly indicated. Alkyl fatty acid esters having C₆-C₂₂ in the fatty acid component and C₁ -C₄ in the alkyl component arefirst reacted in alkaline medium with one or more isopropylidenederivatives of a polyglycerol to form isopropylidene polyglycerol fattyacid esters.

Reaction conditions for producing the intermediate fatty acid esters ofisopropylidene polyglycerols are disclosed and claimed in copending andcommonly assigned U.S. patent application Ser. No. 07/357,006, filed oneven date herewith, now U.S. Pat. No. 5,024,787, and corresponding toGerman P 38 18 292.0, filed May 30, 1988, which is incorporated hereinin its entirety by reference.

The reaction is carried out at temperatures of 140° C.-220° C.,preferably 170° C.-200° C., and in a vacuum of 950-5 mbar, preferably500-10 mbar, and the C₁ -C₄ alcohol which is formed is removed bydistillation, preferably removed continuously, and the resultantreaction product is recovered, preferably purified by filtration,centrifugation, distillation and/or fractional distillation. At leastone isopropylidene group of the reaction product is then cleaved byhydrolysis or alcoholysis, at 20°-100° C., preferably 50° C.-80° C., andat atmospheric, reduced or super-atmospheric pressure, in the presenceof acid.

Suitable alkyl fatty acid esters include, e.g., saturated orunsaturated, branched or unbranched alkyl fatty acid esters, includingesters of forerun C₆ -C₁₀ fatty acids, lauric acid, myristic acid,coconut fatty acid, stearic acid, behenic acid and/or 2-ethylhexanoicacid, isostearic acid, palm oil fatty acid, oil fatty acid, soya oilfatty acid and linoleic acid.

Suitable alkyl hydroxy fatty acid esters include, e.g., ethyl12-hydroxystearate and alkyl ricinoleic acid esters, to name a few thatare readily available commercially.

The isopropylidene derivatives of polyglycerol which are preferably usedare mono- and/or diisopropylidene derivatives of di-, tri- and/ortetraglycerol (with the exception of diisopropylidenediglycerol).

The reaction product is preferably separated after thetransesterification from insoluble components by filtration attemperatures of 20° C.-100° C., preferably 40° C.-70° C.

According to a preferred embodiment, after the reaction of the alkylfatty acid ester, alkyl mono- and/or polyhydroxy fatty acid ester withone or more mono- or diisopropylidene derivatives of di-, tri- and/ortetraglycerol (with the exception of diisopropylidenediglycerol) theexcess of the unconverted alkyl fatty acid ester, alkyl mono- and/orpolyhydroxy fatty acid ester and/or of the unconverted iso- ordiisopropylidene derivatives of di-, tri- and/or tetraglycerol isdistilled off in vacuo, preferably distilled off continuously.

The remaining reaction product, largely fatty acid esters ofisopropylidene polyglycerol, is suspended in an anhydrous or aqueouslower (C₁ -C₆, preferably C₂ -C₄) alcohol, and at least one of theisopropylidene protecting groups is cleaved by hydrolysis and/oralcoholysis, at 20° C.-100° C., preferably 50° C.-80° C., in thepresence of an acid catalyst. After the reaction is completed, thesolvent mixture formed (water, acetone formed, alcohol, acetone-C₁ -C₆-alcohol ketal) is distilled off.

Suitable acids include any strong acid, e.g., mineral acids, organicacids, strongly acidic ion exchange resins, and the like, preferably,mineral acids such as sulfuric acid, phosphoric acid and the like. ThepH of the isopropylidene cleavage reaction is advantageously in therange of about 1-6, preferably about 2-4, especially about pH 3.

The lower alcohol which is used is preferably n-butanol.

The amount of water added to the alcohol, if any, is advantageously 1-5mole per isopropylidene group, preferably 1.1-3.5 mole perisopropylidene group.

Before the solvent is distilled off, it is preferred to neutralizeand/or remove the acid present in the reaction mixture or the acidcatalyst and/or to distill off the solvent mixture. Neutralization canbe effected using any conventional base. According to a preferredembodiment, the neutralization is carried out by addition of a basicanion exchange resin, especially a resin charged with hydroxide ions,and the anion exchange resin is subsequently filtered off.

The invention furthermore relates to the use of certain nonionicpolyglycerol fatty acid ester surfactants, which are preferably preparedby the process according to the invention, as water-in-oil emulsifiers,preferably consisting of at least one vicinal diester of diglycerol orusing them in addition to other surfactants. Vicinal diesters ofdiglycerol are prepared according to the invention from fatty aciddiesters of the mono-isopropylidene derivative of diglycerol, preparedunder conditions which favor formation of the diester (as disclosed inthe companion application incorporated by reference herein), by cleavageof the isopropylidene group.

The invention furthermore relates to the use of certain nonionicpolyglycerol fatty acid ester surfactants, which are preferably preparedby the process according to the invention, as oil-in-water emulsifiers,preferably in the form of the central monoesters of triglycerol and/orthe central mono- and/or diesters of tetraglycerol. Such esters areprepared according to the invention from diisopropylidene derivatives oftriglycerol or tetraglycerol, both of which have a free hydroxyl groupon the central glycerol(s) which can be esterified, after which one orboth of the isopropylidene groups is/are cleaved.

The use of the surfactants refers preferably to their use as additives,wetting agents, dispersants, solubilizing agents, solvents andemulsifiers for skin protection agents and skin care oils, lubricants,textile auxiliary agents, food, detergents and cleaning agents,disinfectants, for biocides, dyes and paints, wood-preservation agentsand for pharmaceutical and/or cosmetic formulations.

According to a preferred embodiment, the vicinal diesters of diglycerolwhich have a diglycerol monoester content of 0.01-40% by weight,preferably 7-25% by weight, (relative to 100 parts by weight of thevicinal diester of diglycerol) are used as surfactants, preferably aswater-in-oil emulsifiers, in skin care or cosmetic formulations.

The invention furthermore relates to skin care and/or cosmeticformulations using at least one nonionic surfactant and water and, ifappropriate, at least one conventional auxiliary, processing agent,consistency-improving agent, stabilizing agent and/or preservative and,if appropriate, at least one conventional fat, wax, oil and/or afat-like substance and/or a perfume, wherein the skin care preparationor cosmetic formulation is (a) an oil-in-water (O/W) emulsion,containing 30-95% by weight of water, preferably 50-88% by weight, thenonionic surfactant being at least one of a surfactant based on a di-,tri- and/or tetraglycerol fatty acid ester, e.g., a di-, tri- ortetraglycerol C₆ -C₂₂ -fatty acid or mono- or polyhydroxy fatty acidester, present as emulsifying agent in an amount of 0.5-10% by weight,preferably 1-6.5% by weight (relative to 100 parts by weight of the skincare and/or cosmetic formulation); or (b) a water-in-oil (W/O) emulsion,containing 20-90% by weight of water, preferably 70-88% by weight, thenonionic surfactant being a vicinal C₆ -C₂₂ -fatty acid or mono- orpolyhydroxy fatty acid diester of diglycerol.

The skin care and/or cosmetic or medicinal formulation according to theinvention, which uses the nonionic surfactant (W/O creams and lotions),leads to occlusive hydration as a result of its occlusive effect on theskin, that is to say, it produces the effect of a humidity chamber byvirtue of a sealing film covering the skin. Water from the emulsionpenetrates into the horny layer lying below. The skin is protected bythe lipid film covering it against evaporation. Polyglycerol esters arespecifically suitable as emulsifiers for the preparation of this type ofW/O emulsion, due to their very good dermatological and toxicologicalproperties.

It is known that a W/O emulsion is formed upon reduction of theinterfacial tension to <5 mN/m and formation of a contact angle betweenoil and water of >90° C. For this, maximum surface tension of theaqueous phase is required. However, water-soluble components in theemulsifier such as diglycerol monoesters and/or higher polyglycerolesters would reduce the surface tension after diffusion into the aqueousphase, that is to say, diminish the contact angle to <90° C. This meansthat the W/O emulsion becomes unstable by partial phase reversal to O/W.

It has now been found that the diglycerol di(fatty acid esters) preparedaccording to the invention, i.e., substantially pure vicinal diglyceroldiesters, and having a defined degree of hydrophilicity (and theformulations prepared therefrom) do not have these disadvantages.

A convenient measure of hydrophilicity these surfactants is the HLBvalue by Griffin.

The vicinal diglycerol di(fatty acid esters) according to the inventionwhich are especially advantageous for forming W/O emulsions with highwater content have a hydrophilicity according to the foregoingmeasurement system of 4.36, preferably 4-4.6.

The different content of water-soluble components in the emulsifier ofthe product according to the invention compared to that of acommercially available product may be illustrated by the followingexample:

Both products were suspended at 1% strength in water at 70° C., cooledand filtered.

Surface tension measured in the filtrate:

    ______________________________________                                        diglycerol diisostearate according                                                                      46 mN/m                                             to the invention                                                              commercial polyglycerol diisostearate                                                                   34 mN/m                                             ______________________________________                                    

However, a drop of the surface tension to 34 mN/m is already in theregion of most O/W emulsifiers.

The commercial polyglycerol diisostearate has the approximatecomposition: polyglycerol condensed from glycerol with approximately twounits of glycerol esterified with two moles of isostearic acid.

Using the diglycerol diisostearate according to the invention, it ispossible to develop stable W/O emulsions, for example for moisturecreams and lotions and also for medicinal purposes. Using substantiallypure vicinal diglycerol di(fatty acid esters), it is possible to preparestable W/O emulsions having a water content of up to 82%.

Another preferred embodiment is a cream which contains 30-90 parts byweight, preferably 50-88 parts by weight of water; 0.5-25 parts byweight, preferably 1-6.5 parts by weight, of the surfactant orsurfactant mixture according to the invention or of a mixture of thesurfactant according to the invention with another surfactant; andoptionally, 0-30 parts by weight, preferably 0.1-25 parts by weight, ofat least one thickening agent, animal and/or vegetable oil, mineral oil,synthetic oil or wax; 0-14.95 parts by weight, preferably 2-14.9 partsby weight, of an organic solvent; 0.05-40 parts by weight, preferably4.1-8.9 parts by weight, of at least one active compound in the form ofat least one skin care active compound, pharmaceutical active compound,local-anesthetic active compound, disinfectant active compound; and/or aperfume or an aromatic substance.

In the foregoing cream, the surfactant is preferably diglyceroldiisostearate.

The other surfactants that can be used in combination therewith in asurfactant mixture include, e.g., diglycerol dioleate.

Advantageously, the amount of the surfactant according to the inventionin such surfactant mixture is at least about 4.5% by weight, preferablyabout 3.2% by weight, more preferably about 1-1.5% by weight.

The invention furthermore relates to a paint or wood-protection agentcontaining at least one binder or binder mixture and a liquid emulsionas the main constituent, said emulsion comprising an organic solvent orsolvent mixture, preferably also using a water-insoluble organic, highlyvolatile solvent or solvent mixture, and water, and containing as anonionic surfactant emulsifier 0.01-10% by weight, preferably 0.1-5% byweight, of at least one of a di-, tri- or tetraglycerol C₆ -C₂₂ -fattyacid or mono- or polyhydroxy fatty acid ester or a vicinal C₆ -C₂₂-fatty acid or mono- or polyhydroxy fatty acid diester of diglycerol,and further comprising at least one of a pigment or pigment mixture, afiller or filler mixture, a dye, and where appropriate a processing aid,a siccative or a biocide.

PREPARATIVE EXAMPLES 1.1 Reaction of methyl oleate withdiisopropylidinetriglycerol

1.52 kg (5 mol) of methyl oleate and 25 g (0.2 mol) of potassiumcarbonate are placed in a 4 1 flask and heated with stirring to about160° C. At a reduced pressure of about 100 mbar, small amounts of waterwhich may be present are distilled off. 820 g (2.5 mol) ofdiisopropylidenetriglycerol are then added, and the reaction temperatureis increased to 180° C.-190° C. At 400-50 mbar, the methanol formed isremoved by distillation. After a reaction time of 4-5 hours, the mixtureis cooled to about 70° C., and precipitated components are filtered off.

Excess alkyl fatty acid ester and unconverteddiisopropylidenetriglycerol are removed by distillation at ≦0.4 mbar anda column head temperature of about 160° C. The remaining crude productis then fine-distilled in a short-path evaporation apparatus at ≦0.1mbar and an oil flow temperature of 210° C.

1.2 Hydrolysis of diisopropylidenetriglycerol monooleate to triglycerolmonooleate

2.5 kg (about 4.4 mol) of diisopropylidenetriglycerol monooleate,prepared by the process described in Preparative Example 1.1, are addedto a mixture of 250 ml of water and 2.01 of n-butanol. The reactionsolution is adjusted to a pH of about 3 by means of 1-molar sulfuricacid, heated to 70° C., and stirred for 4-5 hours. After the reaction iscompleted, OH⁻ -charged anion exchanger is added to the mixture untilthe reaction solution is neutral.

The ion exchanger is filtered off, the filtrate, if necessary, isdecolorized by means of activated carbon, and the low-boiling components(n-butanol, water, acetone formed) are distilled off in vacuo.

2.1 Reaction of methyl palmitate with monoisopropylidenediglycerol

300 g (about 1 mol) of methyl palmitate and 0.5 g of lithium hydroxidemonohydrate are placed in a 2 1 flask and heated with stirring to 160°C. At 150 mbar, the water (from the catalyst and that introduced by thefatty acid ester) is removed by distillation.

1.031 kg (5 mol) of monoisopropylidenediglycerol are then added, and thereaction temperature is increased to 190° C. At 400-50 mbar (lowerpressure toward the end of the reaction), the methanol formed is removedby distillation. After a reaction time of 3 hours, the mixture is cooledto 45° C., and precipitated components are filtered off.

Excess monoisopropylidenediglycerol is removed by distillation at ≦0.2mbar and an oil flow temperature of about 140° C. in a short-pathevaporation apparatus, the remaining crude product is finallyfine-distilled in the same apparatus at ≦0.2 mbar and an oil flowtemperature of 205° C.

2.2 Hydrolysis of monoisopropylidenediglycerol monopalmitate todiglycerol monopalmitate

1.5 kg of monoisopropylidenediglycerol monopalmitate, prepared accordingto the process of Preparative Example 2.1, are added to a mixture of 200ml of water and 2.0 1 of n-butanol. The reaction solution is adjusted toa pH of about 3 by means of 1-molar sulfuric acid, heated to 70° C., andstirred for 4-5 hours. After the reaction is completed, OH⁻ -chargedanion exchanger is added to the mixture until the reaction solution isneutral.

The ion exchanger is filtered off, the filtrate, if necessary, isdecolorized by means of activated carbon, and the low-boiling components(n-butanol, water, acetone formed) are distilled off in vacuo.

FORMULATION EXAMPLES 1. Moisture cream (W/O type):

2.5% of diglycerol diisostearate according to the invention

5.0% of paraffin oil, viscous

5.0% of decyl oleate (Cetiol V, Henkel)

0.7% of Mg stearate

0.3% of Al stearate

4.0% of diglycerol

0.3% of magnesium sulfate heptahydrate

0.1% of Rokonsal CI (Biochema Schwaben)

0.3% of perfume

81.8% of water fully deionized

The formulation is prepared in conventional fashion, as noted above, andthe formulation and preparation are duplicated, except for using as asubstitute for the diglycerol diisostearate according to the inventiontwo commercially available polyglycerol fatty acid ester mixtures of thesame HLB value.

Commercial product 1 has the composition oleic acid polyglycerol ester;

Commercial product 2 has the composition isostearic acid polyglycerolester.

All samples are subjected to conventional storage at 40° C. in a heatingcabinet. The stabilities of the formulations are as follows:

Formulation containing: storage at 40° C.:

Diglycerol diisostearate according to the invention stability>3 months

Commercial product 1: unstable after 12 days

Commercial product 2: unstable after 18 days

2. Skin care cream (W/O type)

4.5% of diglycerol diisostearate according to the invention

6.0% of isopropyl myristate

3.5% of Miglyol 812 neutral oil (Troisdorf-Huels)

6.0% of paraffin oil, viscous

3.0% of vaseline white

4.0% of microwax (Lunacera MW, Fuller)

0.3% of magnesium sulfate heptahydrate

0.1% of Rokonsal CI

0.3% of perfume

72.3% of water fully deionized

The formulation is prepared as in Formulation Example 1, as are theduplicate formulations using the same commercially available productsand tested for stability at 40° C.

Recipe containing: storage at 40° C.:

Diglycerol diisostearate according to the invention stability >3 months

Commercial product 1: unstable after 8 days

Commercial product 2: unstable after 23 days

3. Skin cream (O/W type)

1.5% of triglycerol monoisostearate according to the invention

12.0% of glycerol mono-/distearate

2.0% of cetyl alcohol

5.0% of Cetiol SN (Henkel)

3.0% of acetylated lanolin

10.0% of diglycerol

10.0% of glycerol

0.12% of Carbopol 940 (BF Goodrich)

0.1% of preservative

0.2% of perfume

0.2% of neutralizing agent

55.88% of water fully deionized

Stability in the storage test at 40° C.: >6 months

The foregoing description has been set forth merely to describeillustrative embodiments of the invention and is not intended to belimiting. Since modifications of the described embodiments incorporatingthe spirit may occur to those skilled in the art, the scope of theinvention should be limited solely with respect to the appended claimsand equivalents.

What is claimed is:
 1. A process for preparing a nonionic surfactant,which comprises the steps of:(a) cleaving at least one of theisopropylidene groups of an isopropylidne polyglycerol C₆ -C₂₂ - fattyacid or mono- or polyhydroxy fatty acid ester, said acid or ester beingsuspended in an anhydrous or aqueous C₁ -C₆ alcohol, by hydrolysis orketal exchange, in the presence of acid, at a temperature in the rangeof about 20° C. to about 100° C., and at atmospheric, reduced orsuperatmospheric pressure, thereby regenerating hydroxyl groups on thepolyglycerol; and (b) recovering the resultant polyol ester nonionicsurfactant.
 2. The process of claim 1, wherein said temperature is inthe range of about 50° C. to about 80° C.
 3. The process of claim 1,wherein said alcohol is a C₂ -C₄ alcohol.
 4. The process of claim 3,wherein said alcohol is n-butanol.
 5. The process of claim 1, wherein instep (b), the mixture of solvent alcohol and any of remaining water,acetone formed, and acetone-C₁ -C₆ -alcohol ketal formed is distilledoff, after the reaction of step (a) is substantially completed.
 6. Theprocess of claim 5, wherein the acid catalyst present in the reactionmixture of step (a) is neutralized or removed before said mixture ofsolvent alcohol and any of remaining water, acetone formed, andacetone-C₁ -C₆ -alcohol ketal formed is distilled off.
 7. The process ofclaim 6, wherein the neutralization is carried out by addition of ananion exchanger, and the anion exchanger is subsequently filtered off.8. The process of claim 1, wherein said acid is a strong organic acid ora mineral acid.
 9. The process of claim 1, wherein the pH in step (a) isin the range of about 1 to about
 6. 10. The process of claim 9, whereinsaid pH is about
 3. 11. A process for preparing a nonionic surfactant,which comprises the steps of:(a) cleaving at least one of theisopropylidene groups of a vicinal diester of isopropylidene diglycerol,by hydrolysis or ketal exchange, in the presence of acid, at atemperature in the range of about 20° C. to about 100° C., and atatmospheric, reduced or superatmospheric pressure, thereby regeneratinghydroxyl groups on the vicinal diester of isopropylidene; and (b)recovering the resultant polyol ester nonionic surfactant, saidsurfactant being a substantially pure vicinal diester of diglycerolcontaining 0.01-40% by weight of diglycerol monoester.
 12. The processof claim 11, wherein said content of diglycerol monoester is 7-25% byweight.
 13. A process for preparing a nonionic surfactant, whichcomprises the steps of:(a) cleaving at least one of the isopropylidenegroups of a monoester of diisopropylidene triglycerol, by hydrolysis orketal exchange, in the presence of acid, at a temperature in the rangeof about 20° C. to about 100° C., and at atmospheric, reduced orsuperatmospheric pressure, thereby regenerating hydroxyl groups on themonoester of diisopropylidene triglycerol; and (b) recovering theresultant polyol ester nonionic surfactant, said surfactant being asubstantially pure monoester of triglycerol, the ester beingsubstantially only on the central glycerol moiety thereof.
 14. A processfor preparing a nonionic surfactant, which comprises the steps of:(a)cleaving at least one of the isopropylidene groups of a monoester,diester or mixture of monoester and diester of diisopropylidenetetraglycerol, by hydrolysis or ketal exchange, in the presence of acid,at a temperature in the range of about 20° C. to about 100° C., and atatmospheric, reduced or superatmospheric pressure, thereby regeneratinghydroxyl groups on the polyglycerol; and (b) recovering the resultantpolyol ester nonionic surfactant, said surfactant being a substantiallypure monoester, diester or mixture of monoester and diester oftetraglycerol, the esters being substantially only on the centralglycerol moieties thereof.